Different typefaces have different visual characteristics. Each requires the eye to focus and scan differently, requiring the brain to use different processing capabilities. Similarly, reading a typeface in different colors, or against different backgrounds, necessitates a change in both optical and cognitive functions. Besides taking away from the mental reserves available for cognition, such changes are tiring, and can significantly reduce reader energy. Although an eye-catching change of font may be used effectively, good design should aim for overall consistency. Consistency of type design conveys a sense of consistency of organization and purpose, and this can be used to direct mental challenges to more appropriate places.